sinπ/12-√3cosπ/12=2[(1/2)*sin(π/12)-(√3/2)*cos(π/12)]=2[sin(π/12)cos(π/3)-cos(π/12)sin(π/3)]=2sin(π/12 - π/3)=2sin(-π/4)=-2sin(π/4)=-根号2
sinπ/12-√3cosπ/12=2cos75°=（√2-√6）/2
